26,781 patients who had been prescribed mianserin and 42,082 prescribed amitriptyline were followed up by means of a questionnaire addressed to their general practitioners. No patient had aplastic anaemia, agranulocytosis, or leucopenia severe enough to endanger life, and in only 2 patients in each group was a causal association likely. If either drug dose cause leucopenia, the incidence is likely to be in the range of 1 in 10,000 to 1 in 100,000 patients. Among patients who were reported to have attempted suicide, 56 of 246 survivors of amitriptyline overdoses required intensive care, compared with none of 92 patients who overdosed with mianserin. 4 patients who overdosed with amitriptyline alone died, compared with none of the patients who overdosed with mianserin alone. Both drugs are associated with a low risk of blood disorders, but mianserin is appreciably safer than amitriptyline because of its low toxicity in overdosage.